Quote:
Originally Posted by Isaac Zachary
Most people brake and slow down in just a few seconds. No lithium ion battery can charge from, say 25% to 75% in that amount of time. So a lithium ion battery has to be made bigger, which adds to weight and cost, and the extra size doesn't really help with anything other than extending the life of the battery unless you go engine braking down a long hill.
Also batteries tend to charge up as fast as or slower than they can discharge. With a system that quickly charges up and slowly discharges it would be nice to have something like a super capacitor that can charge as fast as need be and still be sized to whatever capacity makes sense for stoping from 80mpg to 0.
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Capacitors are good for that usage but the problem is that only allows for start / stop function. It doesn't have enough energy storage to provide a boost for acceleration or run HVAC while the vehicle is stopped. Customers hate that type of system and often turn them off. (Nothing like sitting at a light on a nice hot and muggy Alabama day and having the HVAC blow hot air at you.)
(The EPA requires a stop / start system provide 1 minute of heat on a 30F day. There is no requirement to provide A/C with engine off.)